Sodium carbonate chemical formula is Na2CO3, the common name of soda ash, soda, alkali, washing alkali, under normal circumstances for white powder, a strong electrolyte. The density is 2.532g/cm3, the melting point is 851°C, easily soluble in water, with the commonness of salt, is a weak acid salt, slightly soluble in anhydrous ethanol, insoluble in propanol, soluble in water after hydrolysis reaction, making the solution alkaline, has a certain corrosion, can neutralize with acid, generate the corresponding salt and release carbon dioxide. It decomposes at high temperatures to form sodium oxide and carbon dioxide. Long-term exposure to the air can absorb water and carbon dioxide in the air, generate sodium bicarbonate, and form hard. It is very hygroscopic, easy to form hard, and does not decompose at high temperatures. Sodium carbonate and water form Na2CO3·10H2O, Na2CO3·7H2O, and Na2CO3·H2O three kinds of hydrates, among which Na2CO3·Chemicalbook10H2O is the most stable, and the heat of solution in water is very small. Used in the photographic industry, its trade name is carbon oxygen. Na2CO3·10H2O is also known as crystal alkali, which is easily weathered in dry air, and crystal alkali was often used for household washing and wool washing before, so it is also known as "washing alkali". In the past, our people used to use both laundry and dough "block alkali", which was made with soda ash and a lot of water (plus some baking soda (NaHCO3)), and its water content was more than 50%. Sodium carbonate is endothermic when dissolved in water and easily weathered in air. Na2CO3·7H2O is unstable and can only be precipitated from sodium carbonate saturated solution in the range of 32.5 ~ 36℃. Sodium carbonate is a weak acid and a strong alkali salt (soda ash is a salt, not a base, but the solution is strongly alkaline). Na2CO3 produced by chemical methods is purest than trona, so people call it "soda ash".